Directly heated rotary drying drum



United States Patent I l l I Inventors Appl No. Filed Patented AssigneePriority Gerhard Jahn Hoflnungsthal;

Jakob l-Iinterkeuser, Menden, Germany 784,008

Dec. 16, 1968 Nov. 24, 1970 KIockner-l-Iumboldt-Deutz Aktiengesellschaft Cologne-Deutz, Germany a corporation of Germany Dec. 21, 1967Germany No. K64,279

DIRECTLY HEATED ROTARY DRYING DRUM 6 Claims, 3 Drawing Figs.

[52] US. Cl 263/33 [51] Int. Cl F27b 7/00 [50] Field of Search...263/I9C, 32, 33

[56] References Cited UNITED STATES PATENTS 1,860,738 5/1932 Harty etal. 263/33 1,961,314 6/1934 Wall 263/33X Primary Examiner-John J. CambyA1t0mey-Singer,Stern & Carlberg ABSTRACT: An unlined rotary drying drumprovided at one end with a replaceable cylindrical sheet metal shelltherein which extends within the range of an open flame used forheating.

Patented Nov. 24, 1970 3,542,348

IN VE N TOPS 6e rka'ral Jd 12 5? 7 111126 Hz'nterkezzser w mw fliforneysDIRECTLY HEATED ROTARY DRYINGDRUM The invention relates to improvementsin drying drums having 21 directly heated unlined rotary tube, one endof which forms the combustion chamber for an open flame.

The inner jacket for such drums is usually made of sheet steel and inthe range of the flame is particularly subjected to the corrosive anderosive effects of the material being dried.

In the interest of a drum having a short length, there is frequentlyprovided a direct heating, i.e. one end of the drum is constructed as acombustion chamber for an open flame. In such a case the corrosiveattack on the inner jacket of the drum is particularly severe throughoutthe range of the flame length. Added thereto is the erosive effect ofthe drying goods which is especially active in the range of the flamewhen hard,

sharp-edged goods, such as gravel, are dried by the continuous I flowprocess. In a drum structure of this type, the material is introducedinto the drum in the range of the flame and experience has shown thatthis can leadto heavy wear on that portion of the jacket that is mostexposed to the flames. The repair of a drum which'is burnt through,however, is time consuming and costly. Also, in most cases the damage isonly discovered when it becomes visible at the exterior insulation ofthe drum. When this occurs, an immediate suspension of all operationsbecomes necessary.

The object of the invention is an improved drying drum whose rotarycylinder is protected against the corrosive action of the flames. In theevent of wear, the protective means can be quickly exchanged.

This object is attained by providing the drum with a separatecylindrical steel metal shell which is insertable in one end of therotary tube and is positioned close to the interior wall thereof andextends along the range of the length of the flame.

Such a sheet metal shell can be stored as a spare part and mayconveniently be exchanged during a pause in operations when, accordingto experience, the life of the shell in use draws to a close. Inaddition to this advantage, which is important for a continuousproduction process, it will be noted that no particular demands as toquality are made on the material of the replaceable shell, so that theexpense for the initial installation and the spare parts may be keptlow.

The replaceable sheet metal shell may be inserted in the rotary tube ofthe drum with a loose sliding fit. This results in small points orlarger areas of contact between the inner wall of the rotary tube andthe outer wall of the replaceable sheet metal shell so that heat istransferred to the rotary tube. Still more advantageous is the provisionof an air cushion between the rotary tube and the replaceable sheetmetal shell, whereby the enclosed air acts as an additional insulationagainst heat loss.

According to another feature of the invention, cool air may beintroduced into the space between the inner wall of the rotary tube andthe inserted shell, thereby intensively cooling the replaceable shelland thus prolonging its life. In order to utilize for the drying processthe amount of heat absorbed by the cooling air, provision is made thatthe heated air is introduced into the drying drum by an open outlet ofthe intermediate space between the rotary tube and the shell whichoutlet opens toward the rotary tube. The cooling air may also beconsidered part'of the mixed air. The cooling air is supplied to therotary tube in any conventional manner by blowing or suction through asuitably formed inlet opening. The open outlet of the space betweenrotary tube and sheet metal shell is so shaped in view ofthe axialdirection of the movement of the drying goods that the latter areprevented from entering into the intermediate space.

The drawings illustrate in each of the FIGS. 1, 2 and 3 in longitudinalsection a different example of the drying drum according to theinvention.

Referring to FIG. 1, a rotary tube 1 is in known manner mounted at 4 tobe rotatable about its horizontally disposed longitudinal axis. It isslowly rotated by a not illustrated drive mechanism. lntothe right handend of the rotary tube 1, which serves as a combustion chamber, extendsa flame 2 furnished by a nozzle 2a of the drum heating. A tubular sheetmetal shell 3 is inserted into the rotary tube 1 in the range of theflame 2 in such a manner that it is easily removable, tie. it can bepulled out of the rotary tube 1 in an axial direction. The outerdiameter of the tubular sheet metal shell 3 is smaller than the innerdiameter of the rotary tube 1 an amount such that there is formed anintermediate annular space 5 between the two parts I and 3. The air inthe annular space 5 acts as an insulating layer and protects the innerwall of the rotary tube in the range of the flame against thetemperatures that are particularly high in this region. This air spaceaccording to FIG. 2 may be sealed at both ends by heat resistant members9 and 10 to form a closed annular air chamber 11 acting as a cushion.

Still more effective is the introduction of cool air into theintermediate annular space 5. For this purpose, there is provided nearthe right-hand end of the shell 3 an inlet opening 6. The cooling airconveyed in a not illustrated manner by high pressure or -by suctionabsorbs heat and enters the drying drum at a high tempernture by way of,for example, an open outlet 7. If the outlet 7 is arranged in the rangeof the flame, the heated cooling air may be also be used as mixed airfor supporting the combustion. In both cases the heat economy of theprocess is improved by reducing the exterior losses of heat.

The tubular sheet metal shell 3' may also slidably engage the inner wallof the tube 1 as shown in FIG. 3,

In the illustrated embodiments, the charging of the drum with dryinggoods takes place at the end where the heating is provided, i.e. thematerial to be dried is introduced at 8 and then moves in the samedirection as the heating gases in the rotary tube 1, toward the left. Itis, however, within the scope of the invention to modify the proposedarrangement so as to obtain a drying drum for counterflow operation.

We claim:

1. A drying drum provided with a directly heated unlined rotary tube,one end of which forms the combustion chamber for an open flame,including means or producing an open flame, a separate cylindrical sheetmetal shell which is detachably mounted in said rotary tube and extendsclose to the inner wall thereof and within the range of said flame, andmeans for introducing the material to be dried into said separatecylindrical sheet metal shell at the end thereof where the flame isarranged.

2. A drying drum according to claim 1, including means for providing aninlet opening for admitting cool air to an annular space between theinner wall of said rotary tube and said sheet metal shell.

3. A drying-drum according to claim 1, including means for providing aninlet opening for admitting cool air to an annular space between theinner wall of said rotary tube and said sheet metal shell, and an outletopening for said annular space which opens into said rotary tube.

4. A drying drum provided with a directly heated unlined rotary tube,one end of which forms the combustion chamber for an open flame,including means for producing an open flame, a separate cylindricalsheet metal shell which is detachably mounted in said rotary tube, theouter circumference of said sheet metal shell being in slidableengagement with the inner wall of said rotary tube and extending intothe range of said flame.

5. A drying drum accordingto claim 4, including contact areas ofdifferent size between the inner wall of said rotary tube and the outercircumference of said sheet metal shell.

6. A drying drum according to claim 4, in which the outer circumferenceof said cylindrical sheet metal shell is spaced from the inner wall ofsaid rotary tube to form an annular space between said shell and tube,and means sealing the ends of said annular space to form a closedannular air cushion therein.

